Collection tank

ABSTRACT

A collection tank for use in a vacuum operated earth reduction system, the collection tank comprising a closed first end, an open second end defining a tank sealing flange and a body extending between the closed first end and the open second end. An internal chamber defined by the body, the closed first end and the open second end has a door coupled to the open second end and is configured to releasably seal the open second end. An automated door closer is coupled to a center of the door, wherein the automated door closer provides a closing force at the center of the door so that the closing force is equally distributed about a periphery of the door to seal the door against the tank sealing flange.

CLAIM OF PRIORITY

This application is a continuation of U.S. application Ser. No.13/751,987, filed Jan. 28, 2013, which is a continuation of U.S.application Ser. No. 12/979,114, filed Dec. 27, 2010 (now U.S. Pat. No.8,360,260), which is a continuation of U.S. application Ser. No.12/855,478, filed Aug. 12, 2010 (now abandoned), which is a continuationof U.S. application Ser. No. 11/544,428, filed Oct. 6, 2006 (now U.S.Pat. No. 7,837,050), the entire disclosure of each of which isincorporated by reference herein.

FIELD OF THE INVENTION

This invention relates generally to a reduction system for removing soilto expose underground utilities (such as electrical and cable services,water and sewage services, etc.), and more particularly to an improvedvacuum tank for use with such system.

BACKGROUND OF THE INVENTION

With the increased use of underground utilities, it has become morecritical to locate and verify the placement of buried utilities beforeinstallation of additional underground utilities or before otherexcavation or digging work is performed. Conventional digging andexcavation methods such as shovels, post hole diggers, poweredexcavators, and backhoes may be limited in their use in locating buriedutilities as they may tend to cut, break, or otherwise damage the linesduring use.

Devices have been previously developed to create holes in the ground tonon-destructively expose underground utilities to view. One design useshigh pressure air delivered through a tool to loosen soil and a vacuumsystem to vacuum away the dirt after it is loosened to form a hole.Another system uses high pressure water delivered by a tool to softenthe soil and create a soil/water slurry mixture. The tool is connectedwith a vacuum system for vacuuming the slurry away into a collectiontank. The tank may then be emptied by opening a door on the tank.

Prior art vacuum systems are provided with a tank having a manuallyclosing door that is locked in a closed position by latches, locks orother suitable locking mechanisms. Such devices rely on an operator toapply the proper amount of force to ensure that a tight vacuum seal iscreated between an outer periphery of the door and the edge of the tank.However, if the locking force is applied at two opposing edges of thedoor or to a single point around the periphery of the door, then theclosing force is greatest at the point where the door is locked closed.In an example where the locking points are positioned at 9 o'clock and 3o'clock on the door, the greatest closing force occurs at 9 and 3o'clock with the least closing force occurring at 12 and 6 o'clock. Thatis, as you move away from the locking points, the closing force on theperiphery of the door begins to decrease. While a vacuum seal may becreated, it cannot always be guaranteed especially if the door iswarped.

SUMMARY OF THE INVENTION

The present invention recognizes and addresses disadvantages of priorart constructions and methods, and it is an object of the presentinvention to provide a collection tank for use in a vacuum operatedearth reduction system, the collection tank comprising a closed firstend, an open second end defining a tank sealing flange and a bodyextending between the closed first end and the open second end. Aninternal chamber defined by the body, the closed first end and the opensecond end has a door coupled to the open second end and is configuredto releasably seal the open second end. An automated door closer iscoupled to a center of the door, wherein the automated door closerprovides a closing force at the center of the door so that the closingforce is equally distributed about a periphery of the door to seal thedoor against the tank sealing flange.

In other embodiments, the automated door closer further comprises atleast one hydraulic cylinder having a piston rod in driving engagementwith one of said first and second linkage assemblies, said at least onehydraulic cylinder being configured to move said door between said openfirst position and said closed second position.

In yet another embodiment, a collection tank for use in a vacuumoperated earth reduction system comprises a closed first end, an opensecond end defining a tank sealing flange and a body extending betweenthe closed first end and the open second end. A door is moveably coupledto the tank open second end and defines a sealing flange about aperiphery thereof. The door is configured to releasably seal the tankopen second end. An automated door closer has a cross bar rigidlyattached to a center of the door, the cross bar having a first end and asecond end. A first linkage assembly having a first end is threadedlycoupled to the cross bar first end and a second end is coupled to thebody. A second linkage assembly having a first end is threadedly coupledto the cross bar second end and a second end is coupled to the body. Thethreaded connection between the first linkage assembly first end and thecross bar first end and the threaded connection between the secondlinkage assembly first end and the cross bar second end may be adjustedto change a closing force applied to the center of the door.

In other embodiments, the door may have a generally circular-shaped doorpanel having an outer circumference. Additionally, the generallycircular-shaped door panel may be dome-shaped. In yet other embodiments,the door is biased into the closed second position. An in someembodiments, the automated door closer may be remotely actuated.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a perspective view of a prior art vacuum and backfill system;

FIG. 2 is a perspective view of a prior art key hole drill for use withthe drilling and backfill system of FIG. 1;

FIG. 3 is a perspective view of an earth reduction tool in accordancewith an embodiment of the present invention;

FIG. 4 is bottom perspective view of the earth reduction tool shown inFIG. 3;

FIG. 5 is a partial exploded perspective view of the earth reductiontool of FIG. 4;

FIG. 6 is partial perspective view of the earth reduction tool of FIG. 3in use digging a hole;

FIG. 7 is a side plan view of the earth reduction tool of FIG. 3;

FIG. 8 is a top plan view of the earth reduction tool of FIG. 3;

FIG. 9 is a bottom plan view of the earth reduction tool of FIG. 3;

FIG. 10 is a side section view of the earth reduction tool of FIG. 8taken along lines 10-10;

FIG. 11 is a perspective view of the reduction tool of FIG. 3 in usedigging the hole;

FIG. 12 is a perspective view of an earth reduction tool in accordancewith an embodiment of the present invention in operation;

FIG. 13 is a bottom partial perspective view of the earth reduction toolshown in FIG. 12;

FIG. 14 is a top partial perspective view of the earth reduction tool ofFIG. 12;

FIG. 15 is a bottom plan view of the earth reduction tool of FIG. 12;

FIG. 16 is a top plan view of the earth reduction tool of FIGS. 11 and12 shown with additional extensions;

FIG. 17 is side plan view of the earth reduction tool of FIGS. 11 and 12in use digging a hole;

FIG. 18 is a perspective view of the earth reduction tool of FIG. 12 inuse digging a hole;

FIG. 19 is a perspective view of the drilling and backfill system ofFIG. 1, showing the hole being backfilled;

FIG. 20 is a perspective view of the drilling and backfill system ofFIG. 1, showing the hole being tamped;

FIG. 21 is a schematic view of the hydraulic, electric, water, andvacuum systems of the drilling and backfill system of FIG. 1;

FIG. 22 is a left side perspective view of a tank in accordance with anembodiment of the present invention in operation;

FIG. 23 is a right side partial exploded perspective view of the tank ofFIG. 22;

FIG. 24 is a left side partial exploded perspective view of the tank ofFIG. 22;

FIG. 25 is a right side perspective view of the tank of FIG. 22, shownin the open position;

FIG. 26 is a left side partial perspective view of the tank of FIG. 22,shown in the open position; and

FIG. 27 is a left side elevation view of the tank of FIG. 22, shown inthe closed position.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION

Reference will now be made in detail to presently preferred embodimentsof the invention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation ofthe invention, not limitation of the invention. In fact, it will beapparent to those skilled in the art that modifications and variationscan be made in the present invention without departing from the scopeand spirit thereof. For instance, features illustrated or described aspart of one embodiment may be used on another embodiment to yield astill further embodiment. Thus, it is intended that the presentinvention covers such modifications and variations as come within thescope of the appended claims and their equivalents.

Referring to FIG. 1, a drilling and backfill system 10 generallyincludes a water reservoir tank 12, a collection tank 14, a motor 16, adrilling apparatus 18, and back fill reservoirs 20 and 22, all mountedon a mobile chassis 24, which is, in this embodiment, in the form of atrailer. Trailer 24 includes four wheels 38 (only three of which areshown in FIG. 1) and a draw bar and hitch 40. Drilling and backfillsystem 10 generally mounts on a platform 42, which is part of trailer24. It should be understood that while drill and backfill system 10 isillustrated mounted on a trailer having a platform, the system may alsobe mounted on the chassis of a vehicle such as a truck or car. Further,a chassis may comprise any frame, platform or bed to which the systemcomponents may be mounted and that can be moved by a motorized vehiclesuch as a car, truck, or skid steer. It should be understood that thecomponents of the system may be either directly mounted to the chassisor indirectly mounted to the chassis through connections with othersystem components.

The connection of the various components of system 10 is bestillustrated in FIG. 21. Referring also to FIG. 1, motor 16 is mounted ona forward end of trailer 24, provides electricity to power two electrichydraulic pumps 30 and 172 (FIG. 21), and drives both a water pump 26(FIG. 21) and a vacuum pump 28 (FIG. 21) by belts (not shown). Motor 16is preferably a gas or diesel engine, although it should be understoodthat an electric motor or other motive means could also be used. In onepreferred embodiment, motor 16 is a thirty horsepower diesel engine,such as Model No. V 1505 manufactured by Kubota Engine division ofJapan, or a twenty-five horsepower gasoline engine such as Model CommandPRO CH25S manufactured by Kohler Engines. The speed of motor 16 may bevaried between high and low by a wireless keypad transmitter 108 thattransmits motor speed control to a receiver 110 connected to thethrottle of motor 16.

The water system will now be described with reference to FIG. 21. Waterreservoir tank 12 connects to water pump 26, which includes a lowpressure inlet 44 and a high pressure outlet 46. In the illustratedembodiment, water pump 26 can be any of a variety of suitable pumps thatdelivers between 3,000 and 4,000 lbs/in² at a flow rate of approximatelyfive gallons per minute. In one preferred embodiment, water pump 26 is aModel No. TS2021 pump manufactured by General Pump. Water tank 12includes an outlet 50 that connects to a strainer 52 through a valve 54.The output of strainer 52 connects to the low pressure side of waterpump 26 via a hose 48. A check valve 56 is placed inline intermediatestrainer 52 and low pressure inlet 44. High pressure outlet 46 connectsto a filter 58 and then to a pressure relief and bypass valve 60. In onepreferred embodiment, pressure relief and bypass valve 60 is a ModelYUZ140 valve manufactured by General Pump.

A “T” 62 and a valve 64, located intermediate valve 60 and filter 58,connect the high pressure output 46 to a plurality of clean out nozzles66 mounted in collection tank 14 to clean the tank's interior. A returnline 68 connects a low pressure port 69 of valve 60 to water tank 12.When a predetermined water pressure is exceeded in valve 60, water isdiverted through low port 69 and line 68 to tank 12. A hose 70, storedon a hose reel 73 (FIG. 1), connects an output port 72 of valve 60 to avalve 74 on a digging tool 32 (FIG. 3). A valve control 76 (FIG. 3) at ahandle 78 of digging tool 32 provides the operator with a means toselectively actuate valve 74 on digging tool 32. The valve delivers ahigh pressure stream of water through a conduit 80 (FIGS. 3, 5, 7, and21) attached to the exterior of an elongated pipe 82 that extends thelength of digging tool 32.

Referring to FIG. 3, digging tool 32 includes handle 78 for an operator34 (FIG. 11) to grasp during use of the tool, a head 93 and an elongatedpipe 82 that connects the handle to the head. A connector 84, such as a“banjo” type connector located proximate to handle 78, connects thevacuum system on drilling and back fill system 10 (FIG. 1) to a centralvacuum passage 86 (FIG. 4) in digging tool 32. It should be understoodthat other types of connectors may be used in place of “banjo” connector84, for example clamps, clips, or threaded ends on hose 88 and handle78. Referring to FIGS. 7 and 10, vacuum passage 86 extends the length ofelongated pipe 82 and connects at an end (not shown) to one end of avacuum hose 88 (FIG. 11). The other end of hose 88 connects to an inletport 90 on collection tank 14 (FIG. 11). A second end 86 a of vacuumpassage 86 terminates at an opening 87 by a slanted shoulder 89.

Referring to FIGS. 4 and 5, a fluid manifold 91, located at one side 92of head 93, connects a water conduit 80 to a water feed line 94 (FIGS. 4and 7) formed through head 93. In one embodiment, water feed line 94 isintegrally formed in the head during casting of the head. However, itshould be understood that the water feed line may also be added to thehead after the head is cast. Head 93 contains two sets of a plurality ofnozzles 95 and 96, the first set 95 being angled radially inwardly atapproximately 45 degrees from a vertical axis of the digging tool, andthe second set 96 being directed parallel to the axis of the diggingtool. It should be understood that the angle of first set 95 may beadjusted depending on the application of the digging tool to almost anyangle between 0 and 90 degrees to enhance the digging effect of thetool.

Each nozzle is set in a countersunk hole 102 formed in a bottom surface97 of head 93 such that the end of each nozzle is recessed from bottomsurface 97. In particular, if water feed line 94 is integrally castwithin the head, a plurality of tap holes 103 (FIG. 5) are drilled intobottom surface 97 so that the holes tap into water feed line 94. Next,countersunk hole 102 is concentrically formed with tap hole 103, and thetap hole is threaded. The nozzles are then threadedly attached to thetap hole so that the nozzles are in fluid communication with the waterfeed line.

During use of drilling tool 32, nozzles 95 and 96 produce a spiralcutting action that breaks the soil up sufficiently to minimize cloggingof large chunks of soil within vacuum passage 86 and/or vacuum hose 88.Vertically downward pointing nozzles 96 enhance the cutting action ofthe drilling tool by allowing for soil to be removed not only above aburied utility, but in certain cases from around the entire periphery ofthe utility. In other words, the soil is removed above the utility, fromaround the sides of the utility, and from beneath the utility. This canbe useful for further verifying the precise utility needing service and,if necessary, making repairs to or tying into the utility.

Still referring to FIGS. 4 and 5, an air feed passage 98 is formed inhead 93 and has a first opening 99 at head end 92 and a second opening100 at a second end 101 of head 93. In one preferred embodiment, airfeed passage 98 is integrally formed in head 93 when the head is cast.However, it should be understood that the air feed may also be formedfrom tubing extending from head end 93 to head end 101. In one preferredembodiment, second opening 100 is located at or tangential to bottomsurface 97 and may be formed as a single opening or as multipleopenings.

Traditional vacuum digging tools without an air intake can dig avertical hole approximately 0-20 feet deep. When an air intake isincluded in a vacuum digging tool, the digging depth can be extended toa depth of 50 feet or more in the vertical direction. Traditional vacuumdigging tools may include air slots located proximate to head end 101that extend from an outside surface through the head to an insidesurface proximate vacuum passage first end 86 a. Therefore, when thetool is used to dig a hole, air is pulled from around the head proximatehead end 101. As a result, when tool is used to remove wet viscousmaterial or discrete material of large particulate size, the air slotsare easily clogged, thereby reducing the efficiency and effectiveness ofthe digging tool. To overcome this disadvantage of prior art diggingtools, air intake opening 99 is located distal from head end 101 toprevent clogging or blocking of the air intake. As a result, in thepresent invention, the vacuum pressure may be maintained at the optimumlevel regardless of the digging conditions, and the depth of a hole maybe extended several times the normal depth.

In some embodiments, head 93 may be integrally formed with elongatedpipe 82, and air feed passage first opening 99 may be located anywherealong the length of the elongated pipe, provided the air feed passagefirst opening is located at a position distal from head second end 101.Thus, it should be understood that head 93, whether separate from orintegral with elongated pipe 82, is considered to be a part of theelongated pipe. For purposes of this discussion, distal from the headsecond end may refer to a position anywhere from several inches awayfrom the head second end to a point proximate the elongated body firstend. What should be understood by those of skill in the art is that airintake opening 99 should not be located at any point along head 93 orelongated pipe 82 that would be covered by the material to be removed bythe digging tool. It should also be understood in that some embodiments,digging tool 32 may not come equipped with a water feed system.

Returning to FIG. 11, digging tool 32 may also include a control 106 forcontrolling the tool's vacuum feature. Control 106 may be an electricalswitch, a vacuum or pneumatic switch, a wireless switch, or any othersuitable control to adjust the vacuum action by allowing the vacuum tobe shut off or otherwise modulated. An antifreeze system, generally 190(FIGS. 1 and 2), may be provided to prevent freezing of the water pumpand the water system. Thus, when the pump is to be left unused in coldweather, water pump 26 may draw antifreeze from the antifreeze reservoirthrough the components of the water system to prevent water in the hosesfrom freezing and damaging the system.

Referring to FIGS. 12-18, another embodiment of a digging tool 310 hasan elongated cylindrical body 312 with a first end 314 and an oppositesecond end 316. First end 314 is larger in diameter than pipe second end316 such that the pipe first end is configured to receive the second endof another pipe section (as shown in FIG. 17) to extend the overalllength of the digging tool. In this configuration, the length ofelongated pipe 312 can be extended by the use of extender pipes 312 a(FIG. 17) similar to that in the previously described embodiment.

Referring particularly to FIGS. 13-16, elongated body 312 is formed froman inner pipe 318 and an outer pipe 320 spaced apart from the inner pipeby a gap 322 such that gap 322 generally extends between body first end314 and body second end 316. A plurality of fasteners 324 are located ateach end of elongated body 312 and are positioned to secure outer pipe320 to inner pipe 318. A plurality of through holes 326 are formedthrough outer pipe first end 314 proximate to the end of the pipe. Itshould be understood by those skilled in the art that preferably oneelongated pipe 312 would contain holes 326 and that the holes may becontained anywhere along the length of the pipe so long as the holes aredistal from pipe end 316. That is, extension pipes 312 a would notcontain holes 326 since the holes function as an air inlet for air to befed down the length of elongated pipe 312 through gap 322 to end 316.For purposes of this discussion, distal from head second end 316 mayrefer to a position anywhere from several inches away from the headsecond end to a point proximate the elongated body first end. Whatshould be understood by those of skill in the art is that through holes326 should not be located at any point along elongated cylindrical body312 that would be covered by the material to be removed by the diggingtool. A center cavity 328 (FIGS. 13 and 14) defined by inner pipe 318forms a vacuum passageway that is in fluid communication with vacuumhose 88 (FIG. 12).

Similar to the previous embodiment, a water feed line (not shown) may beattached to the length of the elongated pipe that terminates in a fluidmanifold (not shown). Nozzles (not shown), similar to that in theprevious embodiment, may be in fluid communication with the watermanifold for use in cutting and breaking up of the digging material. Thewater feed line may be formed integrally with the elongated pipe, or aseparate feed line may be attached to the pipe using clamps, adhesive,fasteners, etc.

Referring to FIGS. 1 and 21, vacuum pump 28 is preferably a positivedisplacement type vacuum pump such as that used as a supercharger ondiesel truck. In one preferred embodiment, vacuum pump 28 is a Model4009-46R3 blower manufactured by Tuthill Corporation, Burr Ridge, Ill. Ahose 112 connects an intake of the vacuum pump to a vacuum relief device114, which may be any suitable vacuum valve, such as a Model 215V-H01AQEspring loaded valve manufactured by Kunkle Valve Division, BlackMountain, NC. Vacuum relief device 114 controls the maximum negativepressure of the vacuum pulled by pump 28, which is in the range ofbetween 10 and 15 inches of Mercury (Hg) in the illustrated embodiment.A filter 116 (FIG. 1), located upstream of pressure relief valve 114,filters the vacuum air stream before it passes through vacuum pump 28.In one preferred embodiment, the filter media may be a paper filter suchas those FleetGuard filters manufactured by Cummings Filtration. Filter116 connects to an exhaust outlet 118 of collection tank 14 by a hose120, as shown in FIGS. 1, 11, 12 and 21. An exhaust side 122 of vacuumpump 28 connects to a silencer 124, such as a Model TS30TR Cowl silencermanufactured by PHILLIPS & TEMRO INDUSTRIES of Canada. The output ofsilencer 124 exits into the atmosphere.

The vacuum air stream pulled through vacuum pump 28 produces a vacuum incollection tank 14 that draws a vacuum air stream through collectiontank inlet 90. When inlet 90 is not closed off by a plug 127 (FIG. 1),the inlet may be connected to hose 88 (FIGS. 11 and 12) leading todigging tools 32 or 312. Thus, the vacuum air stream at inlet 90 isultimately pulled through vacuum passages 86 or 328 at distal ends 94 or312 of tool 32 or 312, respectively. Because it is undesirable to drawdirt or other particulate matter through the vacuum pump, a bafflesystem, for example as described in U.S. Pat. No. 6,470,605 (the entiredisclosure which is incorporated herein), is provided within collectiontank 14 to separate the slurry mixture from the vacuum air stream. Dirt,rocks, and other debris in the air flow hit a baffle (not shown) andfall to the bottom portion of the collection tank. The vacuum airstream, after contacting the baffle, continues upwardly and exitsthrough outlet 118 through filter 116 and on to vacuum pump 28.

Referring again to FIG. 1, collection tank 14 includes a discharge door126 connected to the main tank body by a hinge 128 that allows the doorto swing open, thereby providing access to the tank's interior forcleaning. A pair of hydraulic cylinders 130 (only one of which is shownin FIG. 19) are provided for tilting a forward end 132 of tank 14upwards in order to cause the contents to run towards discharge door126. A gate valve 140, coupled to a drain 142 in discharge door 126,drains the liquid portion of the slurry in tank 14 without requiring thedoor to be opened. Gate valve 140 may also be used to introduce air intocollection tank 14 to reduce the vacuum in the tank so that the door maybe opened.

Running the length of the interior of collection tank 14 is a nozzletube 132 (FIG. 21) that includes nozzles 66 for directing high pressurewater about the tank, and particularly towards the base of the tank.Nozzles 66 are actuated by opening valve 64 (FIG. 21), which delivershigh pressure water from pump 26 to nozzles 66 for producing a vigorouscleaning action in the tank. When nozzles 66 are not being used forcleaning, a small amount of water is allowed to continuously dripthrough the nozzles to pressurize them so as to prevent dirt and slurryfrom entering and clogging the nozzles.

Nozzle tube 132, apart from being a conduit for delivering water, isalso a structural member that includes a threaded male portion (notshown) on an end thereof adjacent discharge door 126. When dischargedoor 126 is shut, a screw-down type handle 134 mounted in the door isturned causing a threaded female portion (not shown) on tube 132 to matewith the male portion. This configuration causes the door to be pulledtightly against a sealing flange (not shown) of the collection tank.Actuation of vacuum pump 28 further assists the sealing of the dooragainst the tank opening. Discharge door 126 includes a sight glass 136to allow the user to visually inspect the tank's interior.

Referring again to FIG. 1, backfill reservoirs 20 and 22 are mounted onopposite sides of collection tank 14. The back fill reservoirs aremirror images of each other; therefore, for purposes of the followingdiscussion, reference will only be made to backfill reservoir 22. Itshould be understood that backfill reservoir 20 operates identically tothat of reservoir 22. Similar components on backfill reservoir 20 arelabeled with the same reference numerals as those on reservoir 22.

Back fill reservoir 22 is generally cylindrical in shape and has abottom portion 144, a top portion 146, a back wall 148, and a front wall150. Top portion 146 connects to bottom portion 144 by a hinge 152.Hinge 152 allows backfill reservoir 22 to be opened and loaded with dirtby a front loader 154, as shown in phantom in FIG. 1. Top portion 146secures to bottom portion 144 by a plurality of locking mechanisms 156located on the front and back walls. Locking mechanisms 156 may beclasps, latches or other suitable devices that secure the top portion tothe bottom portion. The seam between the top and bottom portion does notnecessarily need to be a vacuum tight seal, but the seal should preventbackfill and large amounts of air from leaking from or into thereservoir. Front wall 150 has a hinged door 158 that is secured close bya latch 160. As illustrated in FIG. 19, hydraulic cylinders 130 enablethe back fill reservoirs to tilt so that dirt can be off loaded throughdoors 158.

As previously described above, backfill reservoirs 20 and 22 may befilled by opening top portions 146 of the reservoirs and depositing dirtinto bottom portion 144 with a front loader. Vacuum pump 28, however,may also load dirt into back fill reservoirs 20 and 22. In particular,back fill reservoir 22 has an inlet port 162 and an outlet port 164.During normal operation, plugs 166 and 168 fit on respective ports 162and 164 to prevent backfill from leaking from the reservoir. However,these plugs may be removed, and outlet port 164 may be connected toinlet port 90 on collection tank 14 by a hose (not shown), while hose 88may be attached to inlet port 162. In this configuration, vacuum pump 28pulls a vacuum air stream through collection tank 14, as describedabove, through the hose connecting inlet port 90 to outlet port 164, andthrough hose 88 connected to inlet port 162. Thus, backfill dirt androcks can be vacuumed into reservoirs 20 and 22 without the aide ofloader 154. It should be understood that this configuration isbeneficial when backfill system 10 is being used in an area where noloader is available to fill the reservoirs. Once the reservoirs arefilled, the hoses are removed from the ports, and plugs 166 and 168 arereinstalled on respective ports 162 and 164.

Referring once more to FIG. 21, hydraulic cylinders 130, used to tiltcollection tank 14 and backfill reservoirs 20 and 22, are powered byelectric hydraulic pump 30. Hydraulic pump 30 connects to a hydraulicreservoir 170 and is driven by the electrical system of motor 16. A highpressure output line 171 and a return line 173 connect pump 30 tohydraulic cylinders 130. Hydraulic pump 172, mounted on trailer 24, isseparately driven by motor 16 and includes its own hydraulic reservoir174. An output high pressure line 175 and a return line 186 connect pump172 to a pair of quick disconnect couplings 182 and 184, respectively.That is, high pressure line 175 connects to quick disconnect coupling182 (FIGS. 1 and 2) through a control valve 178, and return line 186connects quick disconnect coupling 184 to reservoir 188. A pressurerelief valve 176 connects high pressure line 175 to reservoir 188 andallows fluid to bleed off of the high pressure line if the pressureexceeds a predetermined level. A pressure gauge 180 may also be locatedbetween pump 172 and control valve 178.

Quick disconnect coupling 182 provides a high pressure source ofhydraulic fluid for powering auxiliary tools, such as drilling apparatus18, tamper device 185, or other devices that may be used in connectionwith drilling and backfill system 10. The high pressure line preferablydelivers between 5.8 and 6 gallons per minute of hydraulic fluid at apressure of 2000 lbs/in². Hydraulic return line 186 connects to a quickdisconnect coupling 184 (FIGS. 1 and 2) on trailer 24. Intermediatequick disconnect coupling 184 and hydraulic fluid reservoir 174 is afilter 188 that filters the hydraulic fluid before returning it tohydraulic reservoir 174. While quick disconnect couplings 182 and 184are shown on the side of trailer 24, it should be understood that thecouplings may also be mounted on the rear of trailer 24.

Referring to FIGS. 1 and 2, drilling apparatus 18 is carried on trailer24 and is positioned using winch and crane 36. Drilling apparatus 18includes a base 192, a vertical body 194, and a hydraulic drill motor196 slidably coupled to vertical body 194 by a bracket 198. A highpressure hose 200 and a return hose 202 power motor 196. A saw blade 204attaches to an output shaft of hydraulic motor 196 and is used to drilla coupon 206 (FIGS. 11 and 12) in pavement, concrete or other hardsurfaces to expose the ground above the buried utility. The term couponas used herein refers to a shaped material cut from a continuous surfaceto expose the ground beneath the material. For example, as illustratedin FIG. 11, coupon 206 is a circular piece of concrete that is cut outof a sidewalk to expose the ground thereunder.

Body 194 has a handle 220 for the user to grab and hold onto during thedrilling process. Hydraulic fluid hoses 200 and 202 connect to twoconnectors 222 and 224 (FIG. 21) mounted on body 194 and providehydraulic fluid to hydraulic drill motor 196. A crank 226 is used tomove the drill motor vertically along body 194. Drilling apparatus 18 isa Model CD616 Hydra Core Drill manufactured by Reimann & Georger ofBuffalo, N.Y. and is referred to herein as a “core drill.”

In operation, the location of a hole is determined, and if drillapparatus 18 (FIG. 2) was used to remove a coupon from the site, theuser disconnects vacuum hose 88 from the drill and connects the hose todigging tool handle 78 using banjo connector 84. High pressure waterhose 70 is also connected to valve 74 to provide water to the diggingtool as deemed necessary. As tool 32 is used to dig a hole, it ispressed downwardly into the ground. For larger diameter holes, diggingtool 32 is moved in a generally circular manner as it is presseddownward thereby removing material from a large cross-section area.Slurry formed in the hole is vacuumed by tool 32 through vacuum passage86 (FIGS. 4 and 5) and accumulates in collection tank 26. Once the holeis completed and the utility exposed, the vacuum system can be shutdown, and the operators may examine or repair the utility as needed.

Alternatively, referring to FIGS. 12 and 18, elongated body second end316 may be inserted into the area where a hole is desired. Referring toFIG. 18, as a vacuum stream is pulled up vacuum passage 328, an aircurrent 330 is pulled through gap 322, which is fed through holes 326.The air pulled into vacuum passage 328 from gap 322 allows the vacuumsystem to remove dirt and/or water more efficient and effectively than atool without the additional air flow. Moreover, the placement of airinlet holes 326 distal from the vacuum end ensures that the air streamdoes not become clogged or blocked. It should also be understood thatthe embodiment shown in FIGS. 12-18 may be combined with a water feedline (not shown) and high pressure nozzles (not shown) to deliver highpressure water to body end 316.

After work on the utility is completed, and referring to FIG. 19, theoperator may cover the utility with clean backfill from backfillreservoirs 20 and 22. In particular, trailer 24 is positioned so thatone of backfill reservoirs 20 or 22 is proximate the hole. Hydrauliccylinders 130 are activated, causing the tanks to tip rearward so thatbackfill can be delivered through door 158 into the hole. Once the holeis sufficiently filled, hydraulic cylinders 130 return reservoirs 20 and22 to their horizontal position, and door 158 is secured in the closedposition.

With reference to FIG. 20, operator 34 may use a tamping device 185 totamp the backfill in the hole. Tamping device 185 connects to hydraulicpump 172 through quick disconnect couplings 182 and 184 via hydrauliclines 200 and 202. Tamping device 185 is used to pack the backfill inthe hole and to remove any air pockets. Once the hole has been filed andproperly packed, coupon 206 is moved into the remaining portion of thehole. The reuse of coupon 206 eliminates the need to cover the hole withnew concrete. Instead, coupon 206 is placed in the hole, and grout isused to seal any cracks between the key and the surrounding concrete.Thus, the overall cost and time of repairing the concrete issignificantly reduced, and the need for new concrete is effectivelyeliminated.

Drilling and backfill system 10 can be used to dig multiple holes beforehaving to empty collection tank 14. However, once collection tank 14 isfull, it can be emptied at an appropriate dump site. In emptyingcollection tank 14, motor 16 is idled to maintain a vacuum in tank 14.This allows the door handle to be turned so that the female threadedmember (not shown) is no longer in threading engagement with the malemember (not shown) on nozzle rod 132, while the vacuum pressurecontinuing to hold the door closed. Once motor 16 is shut down, thevacuum pressure is released so that air enters the tank, therebypressurizing the tank and allowing the door to be opened. Once opened,hydraulic cylinders 130 can be activated to raise forward end 132 upwarddumping the slurry from the tank.

Collection tank 14 may also include a vacuum switch and relay (notshown) that prevents the tank from being raised for dumping until thevacuum in the tank has dropped below a predetermined level for door 126to be opened. Once the vacuum in the tank has diminished to below thepredetermined level, tank 14 may be elevated for dumping. This preventsslurry from being pushed up into filter 116 if door 126 can not open.

In an alternate embodiment shown in FIGS. 22-27, collection tank 14 isequipped with a sealing flange 415, a discharge door 426 connected tothe main tank body by a hinge 428, and an automatic discharge doorcloser 400. Automated discharge door closer 400 has two linkageassemblies 430A (FIGS. 22 and 24) and 430B (FIGS. 23 and 25), eachincluding an upper linkage arm, a lower linkage arm, and an actuatingcylinder. For ease of discussion, reference will be made to FIGS. 22,24, 26 and 27 to describe linkage assembly 430A, where all referencenumbers are annotated with a capital “A.” However, it should beunderstood that the same components exist for linkage assembly 430Bshown in FIGS. 23 and 25. Any differences between the linkage assemblieswill be pointed out.

Referring to FIG. 24, a lower linkage arm 434A has a lower edge 479A anda first end 435A rigidly connected to a linkage assembly pivot bar 438at the pivot bar's first end 440A. Pivot bar 438 extends from its firstend 440A through the outer wall of collection tank 14 and into aninternal chamber 414. The pivot bar has a longitudinal axis 442 orientedgenerally parallel to a diameter of the collection tank 14. The pivotbar extends along its axis 442 through the tank internal chamber 414 andfurther extends through the opposite side of the collection tank outerwall and terminates at a pivot bar second end 440B (FIGS. 23 and 25). Inone preferred embodiment, a sealed bearing 444A rotatably engages pivotbar 438 at the point where the pivot bar passes through the collectiontank external wall to ensure that tank internal chamber 414 remainssealed from the outside atmosphere. The rigid connection of lowerlinkage arm first ends 435A (FIGS. 24) and 435B (FIG. 25) withrespective first and second pivot bar ends 440A (FIGS. 24) and 440B(FIG. 25) entrains both of the lower linkage arms with the pivot bar sothat the lower linkage arms rotate in unison with the pivot bar.

First lower linkage arm 434A has a second end 437A and an actuatingcylinder mounting hole (not shown) intermediate its first and secondends. In one preferred embodiment, actuating cylinder 436A is ahydraulic cylinder having a cylinder housing 446A and a piston rod 448Athat is slidably received in housing 446A. Piston rod 448A has a freeend 450A that is adapted for pivotal attachment to the lower linkage armcylinder mounting hole. Preferably, a pin connection 451A pivotallyattaches piston rod free end 450A to the cylinder mounting hole (notshown) by a clevis, eyebolt or other similar pivotal linkage.

A pivot pin 439A pivotally connects first lower linkage arm second end437A with a first end 431A of an upper linkage arm 432A. Upper linkagearm 432A has a second end 433A that adjustably receives a threadedportion of an eye bolt 452A. Eye bolt 452A has an eye (not shown) thatis pivotally connected to a first end 454A of a cross bar 456. Thus, thethreaded connection between upper linkage arm second end 433A and crossbar first end 454A allows for adjustment of the space between the upperlinkage arm second end and the cross bar first end.

Referring to FIG. 26, cross bar 456 is rigidly mounted to discharge door426 by means of an attachment cylinder 460. Door 426 has a door panel425 that is preferably dome-shaped, and attachment cylinder 460 islocated on the interior surface of discharge door panel 425 directlyopposite the center or origin of the exterior surface of the door panel.As described in further detail below, the location of attachmentcylinder 460 at the center (origin) of the door panel helps maximize thestrength of the seal when the discharge door if fully closed. In onepreferred embodiment, attachment cylinder 460 receives a bolt 462 thatpasses through both the attachment cylinder and dome-shaped door panel425 and is securely fastened to cross bar 456 by a nut 464 (FIG. 22). Asecondary disk 466 reinforces the connection between the attachmentcylinder 460 and door 426 to prevent the dome-shaped discharge doorpanel 425 from dimpling or deforming when door 426 is sealed againstcollection tank sealing flange 415. It should be understood that doorpanel 425 may be flat, concave or convex as shown in the figures and theshape is based on the application of the door.

Referring to FIGS. 24, collection tank 14 is depicted with dischargedoor 426 in a fully opened position. Automated linkage assembly 430A and430B (FIG. 25) and pivot bar 438 cooperate with hinge 428 to rotatedischarge door 426 into and out of sealing engagement with collectiontank flange 415. When closing the discharge door from its fully openposition, actuating cylinder 436A retracts piston rod 448A. The pivotalpin connection 451A between piston rod free end 450A and lower actuatingarm 434A forces lower actuating arm 434A and therefore pivot bar 438 topivot so that lower actuating arm second end 437A rotates in thedirection of arrow 470.

Referring to FIG. 25, the rigid connection between the second loweractuating arm first end 435B and pivot bar second end 440B forces secondlower actuating arm 434B to rotate in the direction of arrow 471 inresponse to the retraction of actuating cylinder 436A (FIG. 24).Additionally, an actuating cylinder 436B, connected similar to actuatingcylinder 436A, may simultaneously retract a piston rod 448B as actuatingcylinder 436A retracts its piston rod, resulting in increased closingforce applied to lower actuating arms 434A and 434B and pivot bar 438.Actuating cylinders 436A and 436B represent a system redundancy becausethe actuation of either actuation cylinder forces both lower actuatingarms to rotate due to their rigid attachment to pivot bar 438.Accordingly, one of the actuating cylinders may be omitted withoutaltering the function of the automated door. Moreover, should one of theactuating cylinders fail during operation, the other can operate theopening and closing of the door so as to maintain the functionalintegrity of the system. It should be understood that the loweractuating arms do not necessarily need to be rigidly attached to pivotbar 438 but instead may be rotatable with respect to the pivot bar.Thus, in this configuration, each actuating cylinder would drive itsrespective lower actuating arm.

In operation and referring to FIGS. 24 and 25, as the lower actuatingarms rotate in response to the retraction of one or more of the cylinderpiston rods, first and second lower actuating arm second ends 437A and437B exert a downward force on upper actuating arm first ends 431A and431B, through pivot pins 439A and 439B. The downward force applied onupper actuating arm first ends 431A and 431B pulls the upper actuatingarms downward and away from the collection tank open end causing upperactuating arm second ends 433A and 433B to pull cross bar 456 downwardin the direction of arrow 472. As the cross bar travels in the directionof arrow 472, the rigid connection between cross bar 456 and dischargedoor 426 forces door hinge 428 to pivot the door into closing engagementwith collection tank sealing flange 415. Discharge door 426 has a flange427 about its outer periphery that forms a sealed engagement withcollection tank flange 415 once the discharge door fully closes. Itshould be understood that a gasket (not shown) may be attached to one oftank flange 415 or door flange 427 to assist in forming an airtight sealwhen the door in the closed position.

Referring to FIG. 27, once discharge door flange 427 seals with tankflange 415, actuating cylinder 436A continues to retract piston rods448A. As the piston rod further retracts, lower actuating arm second end437A enters into its respective seating bracket 474A and. Seatingbracket 474A has a recess 476A with a bottom seat surface 478A. When thelower actuating arm has rotated sufficiently to bring its lower edge479A into contact with seat surface 478A, the contact between theactuating arm lower edges and the seat surface prevents further rotationof the lower actuating arms. The same holds true for linkage assembly430B on the opposite side of tank 14.

Seating bracket 476A is preferably positioned such that lower actuatingarm lower edge 479A contact seat surface 478A only when pivot point 439Ais located at a position below a horizontal line 480 that intersects thepivot bar longitudinal axis 442. This condition is commonly referred toas “rotation beyond overcenter,” and FIG. 27 shows automated linkageassembly 430A when placed in this position. Because of the entrainedmovement of both automated linkage assembly 430A and automated linkageassembly 430B, both linkage assemblies respond identically as theyrotate beyond overcenter. In this position, door 26 is biased in theclosed position and will remain in the closed position should actuatingcylinders 446A and 446B fail. That is, because pivot points 439A and439B are rotated beyond overcenter, lower actuating arms 434A and 434Bcannot rotate in a direction opposite arrows 470 (FIGS. 24) and 471(FIG. 25) unless they are actively biased in those directions to a pointabove line 480. As a result, in this position, the door is consideredbiased into the closed position since an active force must bias thelower actuating arm pin connections back overcenter into the openposition.

When opening door 426 from its closed position, actuating cylinder 436Aextends piston rod 448A upward causing pivot point 439A to rotate in adirection opposite to arrow 470 above center line 480. This rotationcause upper actuating arm 432A to move rearward toward the tank open endcausing door 426 to pivot upward on hinge 428. As lower actuating arm434A rotates, pivot bar 438 also rotates causing linkage assembly 430Bto move similar to that of linkage 430A. Additionally, actuatingcylinder 436B (FIG. 25) may simultaneously extend piston rod 448B asactuating cylinder 436A extends its piston rod 448A, resulting in anincreased opening force applied to lower actuating arms 434A and 434B.Thus, as the lower actuating arms rotate in the opening direction, theupper actuating arms urge cross bar 456, and therefore door 426, totravel opposite the direction indicated by arrow 472 (FIG. 25).

Referring to FIGS. 24 and 25, once door 426 is in the fully openposition, an operator may lock lower actuating arms 434A and 434B in theopen position. Preferably, two bearing brackets 484A and 484B mounted tothe external surface of tank 14 each have a locking pin hole (not shown)sized appropriately to receive an end of a respective locking pin 486Aand 486B. Additionally, the lower actuating arms each have acorresponding locking pin hole 490A and 490B (FIGS. 22 and 23) alsosized appropriately to receive locking pins 486A and 486B. Thus, whenthe actuating cylinders rotate the lower actuating arms into their fullyopen position, lower actuating arm locking pin holes 490A and 490B alignwith the bearing bracket locking pin holes (not shown), and the operatormay insert locking pins 486A and 486B through the two aligned holes. Inthis way, locking pins 486A and 486B secure the lower actuating arms inthe fully open position ensuring that door 26 remains open when tank 14is being cleaned.

Referring to FIGS. 25 and 26, locking pins 486A and 486B are tethered toa safety guard 488A and 488B by a lanyard 489A and 489B so that theoperator will not misplace the locking pins. Safety guards 488A and 488Bperform the dual function of protecting the operator from pinch pointscreated by the articulating automated linkage assemblies 430A and 430Band providing a storage hole 487A and 487B to receive the locking pinswhen not in use.

As previously stated, the above discussion was directed primarily tolinkage assembly 430A. However, one of skill in the art shouldunderstand that the discussion holds equally for linkage assembly 430B.Moreover, while not shown in the figures, one of skill in the art shouldunderstand that automated linkage assemblies 430A and 430B may beoperated by a control panel at the back of the vehicle, at a controlpanel located inside the vehicle or remotely by a wireless or wiredcontrol panel. One or more of these control panels may be provide tooperate the automated assembly.

The above described embodiments of the automated door closer provideseveral advantages. First, rotating the lower actuating arm 434A and434B into the “beyond overcenter” condition maximizes the amount ofsealing force exerted by cross bar 456 upon discharge door 426. Second,placing the lower actuating arms in the “beyond overcenter” conditionensures that the door is maintained in the closed position. However, thecontact between lower actuating arm lower edges 479A and 479B andseating bracket seat surfaces 478A and 478B prevents further rotation inthe direction of arrows 470A and 470B. This arrangement presents asignificant safety advantage.

Another significant advantage of the automated door closer is the factthat it provides an even seal around the entire circumference of thedischarge door. The location of the contact between cross bar 456 anddischarge door 426 at the center of the door panel allows an evenlydistributed force to be applied between the door flange and the tankflange ensuring a tight seal. That is, the location of attachmentcylinder 460 ensures that all compressive closing force applied to thedoor will be located at the center of the door 426. In this way, thecompressive force is transferred uniformly out to the outercircumference of door 426. In prior art designs, the closing force isusually applied to one or two opposite points on the door periphery. Insuch designs, while the closing force ensures a tight seal proximate theconnection points, it fails to ensure a tight seal around the entireperiphery of the door.

It should be appreciated by those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope and spirit of the invention. It isintended that the present invention cover such modifications andvariations as come within the scope and spirit of the appended claimsand their equivalents.

What is claimed is:
 1. A mobile backfill system for collecting material,comprising: a wheeled vehicle chassis; a collection tank mounted to thechassis and comprising a body having a closed end, an open end oppositethe closed end and having a generally circular periphery, a central,generally cylindrical section extending between the closed end and theopen end, and a door having a generally circular periphery and that ispivotable about a first axis between a first position, at which the dooris spaced from the open end of the body, and a second position, at whichthe generally circular periphery of the door seats against the generallycircular periphery of the open end, thereby closing the open end; avacuum pump mounted to the chassis and connected to the collection tankthat draws an air stream through the collection tank for carryingmaterial into the collection tank; and two over center linkages, eachover center linkage extending between a respective first pivotalconnection between the over center linkage and the door and a respectivesecond pivotal connection between the over center linkage and the tankbody.
 2. The system as in claim 1, comprising a cross bar connected tothe door and disposed at a side of the door opposite the collection tankopen end, wherein the over center linkages respectively attach to thecross bar at the respective first pivotal connections at opposite sidesof the cross bar.
 3. The system as in claim 2, comprising a connectionbetween the cross bar and the door that is configured so that theconnection applies, in response to respective closing forces applied tothe cross bar by the over center linkages when the door is in the secondposition, a net force through an axis of the generally cylindricalsection.
 4. The system as in claim 2, wherein the cross bar is rigidlyconnected to the door.
 5. The system as in claim 2, comprising aconnection between the cross bar and the door having a circularperiphery that is concentric with the circular periphery of the doorabout a center of the door.
 6. The system as in claim 1, comprising anactuator coupled between the chassis and the door so that actuation ofthe actuator applies force to the door.
 7. A mobile backfill system forcollecting material, comprising: a wheeled vehicle chassis; a collectiontank mounted to the chassis and comprising a body having a closed end,an open end opposite the closed end and having a generally circularperiphery, a central, generally cylindrical section extending betweenthe closed end and the open end, and a door having a generally circularperiphery and that is pivotable about a first axis between a firstposition, at which the door is spaced from the open end of the body, anda second position, at which the generally circular periphery of the doorseats against the generally circular periphery of the open end, therebyclosing the open end; a vacuum pump mounted to the chassis and connectedto the collection tank that draws an air stream through the collectiontank for carrying material into the collection tank; and two dual armlinkages, each dual arm linkage extending between a respective firstpivotal connection between said dual arm linkage and the door and arespective second pivotal connection between said dual arm linkage andthe tank body, and having a first arm connected to the door at therespective first pivotal connection and a second arm connected to thebody at the respective second pivotal connection, wherein the first armand the second arm are pivotally connected at a respective third pivotalconnection, wherein the two dual arm linkages are arranged on oppositesides of the collection tank so that a second axis extending through thefirst pivotal connections, a third axis extending through the secondpivotal connections, and a fourth axis extending through the thirdpivotal connections are parallel to each other and to the first axis,when the door is in the first position, the first axis, the second axis,and the fourth axis are on a first side of a plane that includes thethird axis and that, when the door is in the second position, alsoincludes the second axis, and when the door is in the second position,the fourth axis is on a second side of the plane, opposite the firstside of the plane.
 8. The system as in claim 7, wherein the collectiontank further comprises a stop that limits movement of the fourth axis onthe second side of the plane in a direction away from the plane.
 9. Thesystem as in claim 7, wherein the collection tank comprises a stopattached to the body that limits movement of the first arm of at leastone of the two dual arm linkages on the second side of the plane in adirection away from the plane.
 10. The system as in claim 7, comprisinga cross bar connected to the door and disposed at a side of the dooropposite the open end, wherein the dual arm linkages respectively attachto the cross bar at the respective first pivotal connections at oppositesides of the cross bar.
 11. The system as in claim 10, comprising aconnection between the cross bar and the door that is configured so thatthe connection applies, in response to respective closing forces appliedto the cross bar by the dual arm linkages when the door is in the secondposition, a net force through an axis of the generally cylindricalsection.
 12. The system as in claim 11, wherein the cross bar rigidlyconnects to the door.
 13. The system as in claim 10, comprising a rigidconnection between the cross bar and the door that has a circularperiphery that is concentric with the circular periphery of the doorabout a center of the door.
 14. The system as in claim 7, comprising anactuator coupled between the chassis and the door so that actuation ofthe actuator applies force to the door.
 15. The system as in claim 14,wherein the actuator comprises a pair of hydraulic cylinders, eachhydraulic cylinder connected between the chassis and a respective saiddual arm linkage.
 16. The system as in claim 7, comprising a cross barrigidly connected to the door and disposed at a side of the dooropposite the collection tank's open end at a connection that has acircular periphery that is concentric with the circular periphery of thedoor about a center of the door, wherein the dual arm linkagesrespectively attach to the cross bar at the respective first pivotalconnections at opposite sides of the cross bar, and a pair of hydrauliccylinders, each hydraulic cylinder connected between the chassis and arespective said dual arm linkage so that actuation of the hydrauliccylinders applies force to the door.
 17. The system as in claim 16,comprising a shaft extending entirely across an interior of the central,generally cylindrical section along an axis passing through the secondpivotal connections.
 18. The system as in claim 17, wherein the shaftengages the dual arm linkages at the respective second pivotalconnections and extends through opposing sides of the tank body.
 19. Thesystem as in claim 11, comprising a pair of hydraulic cylinders, eachhydraulic cylinder connected between the chassis and a respective saiddual arm linkage so that actuation of the hydraulic cylinders appliesforce to the door.
 20. The system as in claim 19, comprising a shaftextending entirely across an interior of the central, generallycylindrical section along an axis passing through the second pivotalconnections.
 21. A mobile backfill system for collecting material,comprising: a wheeled vehicle chassis; a collection tank mounted to thechassis and comprising a body having a closed end, an open end oppositethe closed end and having a generally circular periphery, a central,generally cylindrical section extending between the closed end and theopen end, and a door having a generally circular periphery and that ispivotable about a first axis between a first position, at which the dooris spaced from the open end of the body, and a second position, at whichthe generally circular periphery of the door seats against the generallycircular periphery of the open end; a vacuum pump mounted to the chassisand connected to the collection tank that draws an air stream throughthe collection tank for carrying material into the collection tank; twodual arm linkages extending between respective first pivotal connectionsbetween the respective dual arm linkage and the door and respectivesecond pivotal connections between the respective dual arm linkages andthe tank body; and a shaft extending entirely across an interior of thecentral, generally cylindrical section along an axis passing through thesecond pivotal connections.
 22. The system as in claim 21, wherein theshaft engages the dual arm linkages at the respective second pivotalconnections and extends through opposing sides of the tank.
 23. Thesystem as in claim 21, comprising a cross bar connected to the door at aside of the door opposite the open end, wherein the dual arm linkagesrespectively attach to the cross bar at the respective first pivotalconnections at opposite sides of the cross bar.
 24. The system as inclaim 23, comprising a connection between the cross bar and the doorthat is configured so that the connection applies, in response torespective closing forces applied to the cross bar by the dual armlinkages when the door is in the second position, a net force through anaxis of the generally cylindrical section.
 25. The system as in claim23, comprising a connection between the cross bar and the door that hasa circular periphery that is concentric with the circular periphery ofthe door about a center of the door.
 26. The system as in claim 21,comprising an actuator coupled between the chassis and the door so thatactuation of the actuator applies force to the door.
 27. The system asin claim 22, comprising an actuator coupled between the chassis and thedoor so that actuation of the actuator applies force to the door.